Restore Function()'s expected string representation.

test/mjsunit/regress/regress-2470.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
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@@ skipping 22 matching lines @@
 
 // Test whether block comments are handled correctly.
 assertDoesNotThrow('Function("/*", "*/", "/**/");');
 assertDoesNotThrow('Function("/*", "a", "*/", "/**/");');
 assertThrows('Function("a", "/*", "*/", "/**/");', SyntaxError);
 
 // Test whether line comments are handled correctly.
 assertDoesNotThrow('Function("//", "//")');
 assertDoesNotThrow('Function("//", "//", "//")');
 assertThrows('Function("a", "//", "//")', SyntaxError);
+
+// Some embedders rely on the string representation of the resulting
+// function in cases where no formal parameters are specified.
+var asString = Function("return 23").toString();
+assertSame("function anonymous() {\nreturn 23\n}", asString);